Ferrite loop antenna for vehicle mounting

ABSTRACT

An omnidirectional antenna comprises a radial array of dipoles radially distributed in the horizontal plane over 360*. Each dipole has a coil wound on a ferrite core with the coils being serially connected and wound in mutually aiding electromagnetic relationship. The antenna is supported by an RF amplifier module adaptable to be mounted on a vehicle.

lliie ties ateni Inventor John J. Reidy 105 West Meadow Road, Wilton, Conn.

06897 Appl. No. 31,861 Filed May 1, 1970 Patented Jan. 11, 1972 Continuation of application Ser. No. 709,258, Feb. 29, 1968, now abandoned. This application May 1, 1970, Ser. No. 31,861

FERlRlTE LOOP ANTENNA FOR VEHICLE MOUNTING 4 Claims, 2 Drawing Figs.

US. Cl 343/702, 343/788, 343/867 lnt. Cl HOlq 7/08 l 30d 28d [50] Field of Search 343/787, 788, 908, 702, 867

[56] References Cited UNITED STATES PATENTS 3,447,159 5/1969 Stromswold. 343/742 3,495,264 2/1970 Spears 343/788 3,051,903 8/1962 Morrow... 343/787 3,440,542 4/1969 Gautney 343/788 Primary ExaminerEli Lieberman Attorney-Robert l. Pearlman an RF amplifier module adaptable to be mounted on a vehicle.

PATENTEU JAIN I B72 INVENTOR.

J'orm I REIDY FERRITE LOOP ANTENNA FOR VEHICLE MOUNTING This is a continuation of application Ser. No. 709,258, filed Feb. 29, I968, now abandoned. 1

The present invention relates to antenna systems and more particularly to an omnidirectional, unified, mobile antenna system preferably in miniaturized form.

In conventional mobile antenna systems it is customary to locate the receiving antenna on the vehicle exterior, remote from the RF amplifier, mixer, IF, and detector circuits inside the vehicle, to take advantage of height, minimal interference and other atmospheric advantages. Accordingly, it has been found that the radiofrequency transmission lines connecting the receiving antenna to the filter and RF amplifier circuits are significant sources of loss and noise.

The present invention is directed to the provision of an omnidirectional mobile antenna having a sensitivity and efficiency not obtainable with conventional mobile antenna systems. This is achieved by employing a unique radial array of dipoles distributed in the horizontal plane over 360. Furthermore, each coil of each dipole is electrically connected in series with its adjacent coil, with the coils being wound in mutually aiding electromagnetic relationship. The antennaarray is supported by an RF amplifier module adaptable to be mounted on a vehicle.

It is therefore, an object of the present invention to provide an improved, highly sensitive and efficient omnidirectional antenna system.

It is a further object of the present invention to provide a mobile antenna system in accordance with the preceding object, in which the signal output of the antenna is maintained substantially constant with variation in the orientation of the antenna.

The features of the invention which are believed to be novel are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and method of operation, together with further objects and features thereof may best be understood with reference to the following description taken in conjunction with the accompanying drawings wherein:

FIG. 1 is a perspective view drawn substantially to scale, of an antenna system constructed in accordance with the principles of the present invention in one embodiment thereof, with a portion thereof broken away,

FIG. 2 is an electrical schematic diagram of the antenna system of FIG. 1.

Referring to the drawings, and in particular to FIG. 1, there is shown a miniaturized mobile receiving antenna assembly suitable for mounting on the roof of a vehicle for intervehicle mobile radio communication, comprising an upright omnidirectional antenna supported by a chassis 12 housing an RF amplifier module 14. Chassis 12 is suitably shaped at its lower surface to facilitate the mounting of chassis 12, supporting antenna 10, to the roof of a vehicle in a manner sufficiently secure to withstand mechanical vibration and shock during the course of travel of the vehicle. Furthermore, in order to provide protection from the elements of weather, antenna 10 and chassis 12 are enclosed by an inverted cup-shaped plastic shroud 16 which allows substantially unimpeded transmission of radio signals therethrough.

Electrical power for amplifier module 14 may suitably be provided by the vehicle battery (not shown) which is typically 12 volts DC, via input cable 18. The amplifier signal output from amplifier module 14 is carried from the output of amplifier module 14 to the control panel (not shown), typically located within the vehicle below the dashboard, via output cable 20, where the amplified signal is heterodyned and the difference between the two frequencies is amplified, detected and then visually or aurally presented.

As shown in FIG. 2, amplifier module 14 which comprises band-pass filter circuit 22 and amplifier circuit 24, comprise solid-state components possessing the characteristics of ruggedness, reliability and compactness, thereby enabling module 14 to be packaged in chassis 12, which typically is approximately 1 xlx' inches in size, and to be disposed proximately to antenna 10 as shown in FIG. 1.

Referring to Flg. ll, miniaturized antenna 10, whose overall dimensions are approximately 1 inch high by I it inch wide, is shown to comprise multiple radially arranged dipoles 26 distributed over 360 in the horizontal plane, having equal coil windings 28a,-28f, disposed on respective core arms 30a,- 30f of ferrite core 30, thereby rendering antenna 10 omnidirectional substantially in horizontal plane. Furthermore, the extremities of coil windings 28a,28f are interconnected in end-to-end series relationship as shown schematically in FIG. 2, with the magnetic flux of the combination being in mutually aiding, i.e., additive relationship.

Referring to FIG. 2, one end of coil 28a is connected to ground terminal 32, while the detected signal output of antenna 10 is taken from one end of end coil 28f and applied to band-pass filter circuit 22 via conductor 34. Filter circuit 22 is seen to comprise two L-filter stages, passing frequencies in the commercial broadcast band, i.e., 0.5 to 1.5 megacycles.

It is noted that, since amplifier module 14 is directly connected to coil 28f of antenna 10, the need for a usually required radiofrequency transmission line to couple the output from antenna 10 to the input of band-pass filter circuit 22, is obviated, thereby achieving a substantial increase in the signal-to-noise ratio and efficiency, otherwise attainable.

Input conductor 34 is connected to the junction of capacitor Cin connected to ground 32, and the series arranged of inductor L1 and capacitor C1, with the other end of capacitor C1 being connected to one end of the parallel arrangement of capacitor C2 and L2, while the other end of capacitor C2 and inductor L2 is connected to ground terminal 32. The second L-filter stage comprises serially connected capacitor C3 and inductor L3 having one end thereof connected to the junction of capacitors Cl and C2 and the other end thereof connected to one end of inductor L4 and capacitor C4 connected in parallel, while the other end of capacitor L4 and capacitor C4 is connected to ground terminal 32. The output of band-pass filter circuit 22 is taken from the junction of inductors L3 and L4 and applied to RF amplifier circuit 24 via conductor 36.

Amplifier circuit 24 is a two stage RF amplifier, including first stage N-channel field effect transistor 0, whose output is applied to second stage N-channel field effect transistor 02. The use of field effect transistors in amplifier circuit 24 is particularly advantageous since they have excellent isolation characteristics.

Conductor 36 applies the band-pass filtered RF signal from filter circuit 22 to source electrode 38 of transistor OI, while the parallel arrangement of resistor R1 and capacitor C5 interconnect drain electrode 40 and ground 32. Gate electrode 42 is connected directly to ground 32, while the other drain electrode 44 is connected to bias supply voltage terminal 46 (typically plus 12 volts) via load resistor R2.

The output from first amplification stage transistor ()1 is taken from drain electrode 44 via coupling capacitor C6 and is applied to source electrode 48 of transistor 02, which is connected to input resistor R3 having the other end thereof connected to ground 32.

The second amplication stage comprising transistor 02 is arranged similarly to transistor 01. Thus, drain electrode 50 is connected to ground 32 via resistor R4 and capacitor C7 in parallel, gate electrode 52 is connected directly to ground 32, and drain electrode 54 is connected to supply terminal 46 through load resistor R5. The amplified RF signal output is taken from drain electrode 54 via coupling capacitor C8, and thence to the heterodyning circuitry via output cable 20.

The following circuit constants are illustrative values of the circuit elements of band-pass filter circuit 22 and amplifier circuit 24, which may be utilized in a receiver system operating in the commercial broadcast band of 0.5 to 1.5 megacycles:

Capacitor C 19.7 pf. Inductors LI 8L L3 1.2!] mh. Capacitors Cl & C3 26 pf. Inductor L2 502 uh. Capacitor C2 64 pf. Coils 28n,-28f each 0.24 mh.

Transistors Ol 81. O2 type3N I 39 Resistors Rl & R4 220 ohms Capacitors C5. C6 & C7 0.0l #f. Resistors R2 84 R 2.2 K Resistor R3 100 K Capacitor C8 1000 pf.

While there has been shown a particular embodiment of the present invention it will be understood that it is not wished to be limited thereto, since modifications can be made both in the circuit arrangement and instrumentalities employed and it is contemplated in the appended claims to cover any such modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. An antenna system comprising an omnidirectional antenna and amplifier means in circuit with the output of said antenna, said antenna including a horizontally oriented radial array of loop antennas radially emanating from a central point so as to be distributed in the horizontal plane over 360, said radial loop antenna array comprising a plurality of coils electrically connected in series respectively wound on an equal number of ferrite c'ores arranged in a radial array from a central point in mutually aiding electromagnetic relationship, said coils having a fixed number of active turns, said amplifier taking the form of an amplifier module which forms a base upon which said antenna having horizontally oriented radial array of loop antennas is positioned.

2. The antenna system of claim 1 which is miniaturized so as to be readily mounted on an automobile.

3. The antenna system of claim 1 wherein said amplifier means includes band-pass filter circuit means in circuit with the output of said antenna and RF amplifier circuit means in circuit with the output of said filter circuit means.

4. An antenna system comprising an omnidirectional antenna and amplifier means in circuit with the output of said antenna, said antenna including a horizontally oriented radial array of loop antennas radially emanating from a central point so as to be distributed in the horizontal plane over 360, said radial loop antenna array comprising a plurality of coils electrically connected in series respectively wound on an equal number of ferrite cores arranged in radial array from a central point in mutually aiding electromagnetic relationship, said coils having a fixed number of active turns, and wherein said amplifier takes the form of an amplifier module which forms a base upon which said antenna having a horizontally oriented radial array of loop antennas is positioned. 

1. An antenna system comprising an omnidirectional antenna and amplifier means in circuit with the output of said antenna, said antenna including a horizontally oriented radial array of loop antennas radially emanating from a central point so as to be distributed in the horizontal plane over 360*, said radial loop antenna array comprising a plurality of coils electrically connected in series respectively wound on an equal number of ferrite cores arranged in a radial array from a central point in mutually aiding electromagnetic relationship, said coils having a fixed number of active turns, said amplifier taking the form of an amplifier module which forms a base upon which said antenna having horizontally oriented radial array of loop antennas is positioned.
 2. The antenna system of claim 1 which is miniaturized so as to be readily mounted on an automobile.
 3. The antenna system of claim 1 wherein said amplifier means includes band-pass filter circuit means in circuit with the output of said antenna and RF amplifier circuit means in circuit with the output of said filter circuit means.
 4. An antenna system comprising an omnidirectional antenna and amplifier means in circuit with the output of said antenna, said antenna including a horizontally oriented radial array of loop antennas radially emanating from a central point so as to be distributed in the horizontal plane over 360*, said radial loop antenna array comprising a plurality of coils electrically connected in series respectively wound on an equal number of ferrite cores arranged in radial array from a central point in mutually aiding electromagnetic relationship, said coils having a fixed number of active turns, and wherein said amPlifier takes the form of an amplifier module which forms a base upon which said antenna having a horizontally oriented radial array of loop antennas is positioned. 